The invention relates to optical pickup devices and composite optical devices especially suitable for use in an optical disc system.
Along with the recent diversification of optical disc systems, there has been an increase in incompatible optical discs using what are referred to herein as different read/write formats (or simply formats) (for example, CD, CD-R, MD, MO, Phase Change Disc DVD, and so on). These read/write formats can very, e.g., by using laser light from a semiconductor laser for emitting light in the band of 780 nm, laser light from an emitting semiconductor laser for emitting red light in the band of 635 nm (or 650 nm), laser light from a semiconductor laser for emitting blue light, and so forth. The optical pickup devices used to read from and write to these different optical recording media then have what are referred to herein as different read/write specifications.
In order to use a common optical disc system to record and reproduce signals wit different kinds of optical discs having different formats, a system needs different optical pickup devices for respective optical discs having different read/write formats.
On the other hand, considering the large differences in purpose and characteristics between writing semiconductor lasers and reading semiconductor lasers, it would be easier for making an optical pickup device, in some applications, to use a semiconductor laser only for writing and another semiconductor laser for reading.
However, the use of different optical pickup devices for respective optical discs of different formats invites an increase in the dimensions and cost of the optical disc system. Especially when a packaged writing semiconductor laser and a packaged reading semiconductor laser are used to make up an optical pickup device, the optical pickup device itself, and an optical disc system using it, become more bulky. At the same time, these semiconductor lasers and photodetector elements are difficult to assemble because adjustment of their optical axes is more difficult than conventional devices.
It is, therefore, an object of the invention to provide an optical pickup device that can be used for both reading from and writing to different kinds of optical discs having different read/write formats, and yet has a small-scaled, easily assembled structure.
Another object of the invention is to provide a composite optical device that can be used for both reading from and writing to different kinds of optical discs having different read/write formats when used in an optical pickup device, and contributes to miniaturization and easier assembly of the optical pickup device.
According to a first aspect of the invention, there is provided an optical pickup device comprising:
a plurality of a composite optical devices, each having a light emitting element, a photodetector element and a transparent optical element with a partial reflective plane that are supported on a base body, the composite optical devices having different read/write specifications..
Typically, the light emitting elements are different from each other in light emitting wavelength and/or optical output power. Each light emitting element, photodetector element and transparent optical element typically is arranged so that the optical axis of exist light from the light emitting element and the optical axis of incident light to the photodetector element substantially coincide on the partial reflective plane of the transparent optical element.
According to another aspect of the invention, there is provided a composite optical device comprising:
a plurality of light emitting elements, a photodetector element and a transparent optical element having a partial reflective plane that are provided on a base body, the light emitting elements having different read/write specifications.
Typically, the light emitting elements are different from each other in light emitting wavelength and/or optical output power. Each light emitting element, photodetector element and each transparent optical element are typically arranged so that the optical axis of exit light from the light emitting element and the optical axis of incident light to the photodetector element substantially coincide on the partial reflective plane of the transparent optical device.
The optical pickup device having the above construction according to the invention can be used for both reading of and writing to different kinds of optical discs having different formats by designing its composite optical devices to have specifications in accordance with the different kinds of optical discs. Since the composite optical devices can be miniaturized, the optical pickup device also can be small-scaled. Moreover, since light emitting elements, photodetectors and transparent optical elements in the composite optical devices are previously adjusted in optical axis, etc., the optical pickup device can be assembled easily.
The composite optical device having the above construction according to the invention can be used for both writing to and reading of different kinds of optical discs having different formats by designing individual light emitting elements to have specifications in accordance with the different kinds of optical discs. Since the composite optical device can be miniaturized, a miniaturized optical pickup device can be made by using the optical pickup device. Moreover, since optical axes, etc. of light emitting elements, photodetectors and transparent optical elements in the composite optical devices can be adjusted easily like those of a conventional composite optical device having a single light emitting element, they can be assembled easily.
These and other features of the invention are discussed in greater detail below in the following detailed description of the presently preferred embodiments with reference to the accompanying drawings.